Automotive alternator

ABSTRACT

An automotive alternator secures a fastening force for a vehicular connecting terminal for an extended period of time, and restricts the axial displacement of an output terminal, thus ensuring higher reliability. The output terminal is press-fitted and secured in a through hole in a first cooling plate, and the takeout end thereof is drawn out of an opening of a rear bracket. A metal bush is loosely inserted in an insulating bush and externally fitted to the output terminal, and the vehicular connecting terminal is fasteningly secured to the metal bush by a nut. With this arrangement, the fastening force of the nut is received by the rear surface of the first cooling plate via the metal bush. A flange of the metal bush is positioned so that a gap is provided between the flange and the insulating bush. The axial displacement of the output terminal is restricted by the flange abutting against the insulating bush.

This application is based on Application No. 2000-320952, filed in Japanon Oct. 20, 2000, the contents of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an automotive alternator and, moreparticularly, to an assembly structure of a rectifying unit for anautomotive alternator.

2. Description of the Related Art

FIG. 11 is a perspective view showing a conventional rectifying unitapplied to an automotive alternator. FIG. 12 is a sectional view of anessential section for explaining the conventional rectifying unit, whichhas been installed.

Referring to FIG. 11 and FIG. 12, a rectifying unit 120 includes aplurality of positive-electrode-side diodes 20 andnegative-electrode-side diodes 21 for carrying out full-waverectification on three-phase alternating current, a first cooling plate122 and a second cooling plate 123 for cooling thepositive-electrode-side diodes 20 and the negative-electrode-side diodes21, respectively, insulators 24 and 27 for insulating the first andsecond cooling plates 122 and 123, a circuit board 125, and an outputterminal 26. The positive-electrode-side diode 20 and thenegative-electrode-side diode 21 constitute a first diode and a seconddiode, respectively.

The first cooling plate 122 is shaped like a horseshoe, and has thepositive-electrode-side diodes 20 arranged on a main surface 122 athereof in the circumferential direction. A radiating fin 122 b isvertically installed from the rear surface of the first cooling plate122, that is, the surface opposing the main surface. Three flanges 130,131, 132 are provided at both ends and the middle, respectively, in thecircumferential direction of the first cooling plate 122. All theflanges 130, 131, and 132 are raised from a main surface 101 a of thefirst cooling plate 101, and extended outward in the radial direction.An output terminal insertion through hole 134 is provided in theradially extended end of the flange 130 provided at one circumferentialend of the first cooling plate 122. Mounting screw insertion throughholes 133 are provided in the radially extended ends of the remainingflanges 131 and 132.

The second cooling plate 123, which is also shaped like a horseshoe, hasa larger diameter than that of the first cooling plate 122, and has thenegative-electrode-side diodes 21 arranged on a main surface 123 athereof in the circumferential direction. Furthermore, one outputterminal insertion through hole 138, and two mounting screw insertionthrough holes 135 are provided at both ends and the middle in thecircumferential direction of the second cooling plate 123 such that theyalign with the output terminal insertion through hole 134 and themounting screw insertion through holes 133 provided in the first coolingplate 122, respectively.

The circuit board 125 is a resinous molding having insert-molded wiringfor constituting diode bridges for the positive-electrode-side diodes 20and the negative-electrode-side diodes 21, and horseshoe-shaped like thesecond cooling plate 123. Furthermore, one output terminal insertionthrough hole 137 and two mounting screw insertion through holes 136 areprovided at both ends and the middle in the circumferential direction ofthe circuit board 125 such that they align with the output terminalinsertion through hole 134 and the mounting screw insertion throughholes 133 provided in the first cooling plate 122, respectively.

Each of the cylindrically shaped insulators 24 is made of, for example,a phenol resin, and has a flange 24 a in the central portion of theouter periphery thereof. The cylindrically shaped insulator 27 is madeof, for example, a phenol resin, and has a flange 27 a at one endportion thereof. The output terminal 26 has a knurl groove portion 26 aprovided at the counter-takeout side and an external thread portion 26 bprovided at the takeout side.

The rectifying unit 120 is assembled as described below. First, theinsulators 24 are inserted in the mounting screw insertion through holes135 of the second cooling plate 123 such that the flanges 24 a are incontact with the main surface 123 a. Similarly, the insulator 27 isinserted in the output terminal insertion through hole 138 of the secondcooling plate 123 such that the flange 27 a is in contact with the mainsurface 123 a. Then, the first cooling plate 122 is disposed such thatthe insulators 24 are inserted in the mounting screw insertion throughholes 133. This concentrically arranges the first and second coolingplates 122 and 123, respectively, with their main surfaces 122 a and 123a being flush with each other, and the positive-electrode-side diodes 20and the negative-electrode-side diodes 21 facing each other. The circuitboard 125 is stacked on the main surface 123 a of the second coolingplate 123 such that the insulators 24 are inserted in the mounting screwinsertion through holes 136. Thus, connecting terminals 125 a of thecircuit board 125 are held between terminals 20 a and 21 a of theopposing positive-electrode-side and negative-electrode-side diodes 20and 21, respectively, and joined by soldering. Subsequently, the outputterminal 26 is inserted from the output terminal insertion through hole137 of the circuit board 125 into the output terminal insertion throughholes 134 and 138 of the first and second cooling plates 122 and 123,respectively. Lastly, the knurl groove portion 26 a of the outputterminal 26 is press-fitted into the output terminal insertion throughhole 134 of the first cooling plate 122 to electrically connect theoutput terminal 26 and the first cooling plate 122, completing theassembly of the rectifying unit 120 shown in FIG. 11.

In the rectifying unit 120 assembled as described above, a mountingscrew 40 inserted in the mounting screw insertion through holes 133,135, and 136 is fastened into a tapped hole 2 a provided in a rearbracket 2 so as to fasten together the first and second cooling plates122 and 123, and the circuit board 125, as illustrated in FIG. 12. Thetakeout end of the output terminal 26 connected to the first coolingplate 122 is extended out of an opening 2 b provided in the rear bracket2. An output terminal fastening nut 50 threaded to the external threadportion 26 b of the output terminal 26 is fastened thereby to fastentogether an insulating bush 41 formed of a phenol resin mounted on theopening 2 b of the bracket 2, the first and second cooling plates 122and 123, and the circuit board 125 onto the rear bracket 2.

To join a vehicular connecting terminal 42 to the output terminal 26,the connecting terminal 42 is externally fitted to the takeout end ofthe output terminal 26, and a nut 44 is screwed onto the external threadportion 26 b. Then, the nut 44 is tightened to fasteningly secure theconnecting terminal 42 to the outer end surface of the nut 50. In thiscase the outer end surface of the output terminal fastening nut 50serves as a fastening seat.

The first and second cooling plates 122 and 123, the circuit board 125,and the insulating bush 41 are secured together to the rear bracket 2 bythe fastening force of the output terminal fastening nut 50. With thisarrangement, even if the vibration caused by a weight, such as aharness, is transmitted from the vehicle to the vehicular connectingterminal 42, the output terminal 26 will not be displaced in the axialdirection, thus initially preventing damage or the like to therectifying unit 120. Moreover, since the fastening force of the nut 44is received by the outer end surface of the output terminal fasteningnut 50 making up the fastening seat, the fastening force for thevehicular connecting terminal 42 is initially secured.

In the conventional automotive alternator, since the rectifying unit 120is assembled and installed as set forth above, when power is generatedby the automotive alternator, large current passes the vehicularconnecting terminal 42, generating heat. The generated heat is conductedfrom the nut 50 to the insulating bush 41, and the insulating bush 41becomes hot. This has been posing a problem in that the insulating bush41 develops thermal degradation and shrinks. The shrinkage of theinsulating bush 41 causes loose fastening by the output terminalfastening nut 50, allowing the output terminal 26 to be displaced in theaxial direction. As a result, if the vibration of a weight, such as aharness, from a vehicle is transmitted to the vehicular connectingterminal 42, the output terminal 26 is displaced in the axial direction.This has been giving a rise to a problem in that the rectifying unit 120may be damaged or the fastened portion of the mounting screw 40 maybreak, with consequent degraded reliability.

If the output terminal fastening nut 50 loosens, then the connectingterminal 42 fastened by the nut 44 accordingly becomes loose. Thiscauses markedly increased heat generation at the fastened portion of theconnecting terminal 42, adding to the shrinkage of the insulating bush41 attributed to thermal degradation. Hence, the output terminal 26tends to be axially displaced more readily, leading to a problem in thatthe rectifying unit 120 is damaged or the fastened portion of themounting screw 40 breaks more easily due to the vibrations caused by aweight, such as a harness, from a vehicle, resulting in degradedreliability.

Furthermore, the fastening force of the nut 44 is received by the outputterminal fastening nut 50 pushing the insulating bush 41, posing aproblem in that the vibration of a weight, such as a hardness, from avehicle is repeatedly applied to the insulating bush 41 via the nut 50,causing the insulating bush 41 to develop a creep. The creep of theinsulating bush 41 in turn leads to loose fastening by the outputterminal fastening nut 50, giving a rise to the problem described above.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made with a view towardsolving the problems described above, and it is an object of the presentinvention to provide an automotive alternator having an axialdisplacement restricting member for restricting the axial displacementof an output terminal connected to a first cooling plate of a rectifyingunit, wherein a fastening seat for fastening a vehicular connectingterminal is provided at a takeout end of the output terminal to restraindamage to the rectifying unit attributable to the axial displacement ofthe output terminal and to restrain heat generation attributable toloosening of a fastened portion of the vehicular connecting terminal,thereby achieving improved reliability of the automotive alternator.

It is another object of the present invention to provide an automotivealternator wherein a fastening seat for fastening a vehicular connectingterminal, which is irrelevant to a fixing device, is provided at atakeout end of an output terminal by which first and second coolingplates of a rectifying unit are secured to a bracket, therebyrestraining heat generation attributable to loosening of a fastenedportion of the vehicular connecting terminal so as to achieve improvedreliability of the automotive alternator.

To these ends, according to one aspect of the present invention, thereis provided an automotive alternator including a rotor rotatablysupported in a metal bracket, a stator secured to the bracket such thatit is located around the outer periphery of the rotor to surround therotor, a rectifying unit having a first cooling plate on which aplurality of first diodes are provided, and a second cooling plate onwhich a plurality of second diodes of the opposite polarity from that ofthe first diodes are provided, the second cooling plate beingelectrically connected to the bracket, and the first and second coolingplates being secured to an inner wall surface of the bracket, a resinousinsulating bush mounted at an opening provided in the bracket, an outputterminal which is electrically connected to the first cooling plate,loosely inserted in the insulating bush, and taken out of the bracket, avehicular connecting terminal being connected to the takeout end of theoutput terminal, an axial displacement restricting member which engagesthe insulating bush thereby to restrict the axial displacement of theoutput terminal, and constitutes a fastening seat, and an externalthread portion provided on the takeout end of the output terminal,wherein the counter-takeout end of the output terminal is secured to thefirst cooling plate, and the vehicular connecting terminal isfasteningly secured to the fastening seat of the axial displacementrestricting member by a nut threadably attached to the external threadportion.

Preferably, an elastic member is interposed between the axialdisplacement restricting member and the insulating bush.

Preferably, the insulating bush is mounted at the opening of the bracketsuch that it is abutted against the axial displacement restrictingmember, and the insulating bush is formed of an elastic material.

Alternatively, the axial displacement restricting member is externallyfitted to the output terminal, and composed of a cylindrical metal bushhaving a flange of a large diameter on one end thereof, one end surfaceof the metal bush abuts against the vehicular connecting terminal, andthe other end surface thereof abuts against the first cooling plate, andthe flange thereof engages the insulating bush to restrain the axialdisplacement of the output terminal when the vehicular connectingterminal is connected to the takeout end of the output terminal.

Alternatively, the axial displacement restricting member is constructedby a metal bush fastening nut threadably attached to the external threadportion of the output terminal, a cylindrical metal bush which isexternally fitted to the output terminal and fasteningly secured to thefirst cooling plate by the metal bush fastening nut, the vehicularconnecting terminal is fasteningly secured to the outer end surface ofthe metal bush fastening nut by the nut threadably attached to theexternal thread portion, and the inner end surface of the metal bushfastening nut engages the insulating bush thereby to restrain the axialdisplacement of the output terminal.

Preferably, the axial displacement restricting member is constituted bya large-diameter flange formed at the proximal end of the externalthread portion of the output terminal, the vehicular connecting terminalis fasteningly secured to the outer end surface of the flange by the nutthreadably attached to the external thread portion, and the inner endsurface of the flange engages the insulating bush thereby to restrainthe axial displacement of the output terminal.

Preferably, a support wall is vertically provided such that it opposesthe counter-takeout end surface of the output terminal, and aninsulating member is interposed between the support wall and thecounter-takeout end surface of the output terminal.

According to another aspect of the present invention, there is providedan automotive alternator including a rotor rotatably supported in ametal bracket, a stator secured to the bracket such that it is locatedaround the outer periphery of the rotor to surround the rotor, arectifying unit having a first cooling plate on which a plurality offirst diodes are provided, and a second cooling plate on which aplurality of second diodes of the opposite polarity from that of thefirst diodes are provided, the second cooling plate being electricallyconnected to the bracket, and the first and second cooling plates beingsecured to an inner wall surface of the bracket, a resinous insulatingbush mounted at an opening provided in the bracket, an output terminalwhich is electrically connected to the first cooling plate, looselyinserted in the insulating bush, and taken out of the bracket, avehicular connecting terminal being connected to the takeout end of theoutput terminal, through holes which are provided in the first andsecond cooling plates and in which the output terminal is inserted, anexternal thread portion provided on the takeout end of the outputterminal, an output terminal fastening nut threadably attached to theexternal thread portion to fasteningly secure the output terminal to thebracket, and a fastening seat provided at a position different from thatof the output terminal fastening nut on the takeout end of the outputterminal, wherein the counter-takeout end of the output terminal isinserted in the through holes of the first and second cooling plates andsecured to the first cooling plate, the first and second cooling platesare secured together with the insulating bush to the bracket by theoutput terminal fastening nut, and the vehicular connecting terminal isfasteningly secured to the fastening seat by a nut threadably attachedto the external thread portion.

Preferably, the external thread portion of the output terminal iscomposed of a first external thread portion having a large diameter towhich the output terminal fastening nut is threadably attached and asecond external thread portion having a small diameter which iscontinuously formed at the takeout end of the first external threadportion and to which the nut is threadably attached, and a steppedportion formed in the area, where the first and second external threadportions are connected, constitutes the fastening seat.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features, objects and advantages of the present invention willbecome apparent from the following description of preferred embodimentswith reference to the drawings in which like reference charactersdesignate like or corresponding parts throughout several views, and inwhich:

FIG. 1 is a sectional view showing an automotive alternator according toa first embodiment of the present invention;

FIG. 2 is a perspective view showing a rectifying unit applied to theautomotive alternator according to the first embodiment of the presentinvention;

FIG. 3 is a sectional view of an essential section illustrating anoutput takeout structure in the automotive alternator according to thefirst embodiment of the present invention;

FIG. 4 is a sectional view of an essential section illustrating anoutput takeout structure in the automotive alternator according to asecond embodiment of the present invention;

FIG. 5 is a sectional view of an essential section illustrating anoutput takeout structure in the automotive alternator according to athird embodiment of the present invention;

FIG. 6 is a sectional view of an essential section illustrating anoutput takeout structure in the automotive alternator according to afourth embodiment of the present invention;

FIG. 7 is a sectional view of an essential section illustrating anoutput takeout structure in the automotive alternator according to afifth embodiment of the present invention;

FIG. 8 is a sectional view of an essential section illustrating anoutput takeout structure in the automotive alternator according to asixth embodiment of the present invention;

FIG. 9 is a sectional view of an essential section illustrating anoutput takeout structure in the automotive alternator according to aseventh embodiment of the present invention;

FIG. 10 is a sectional view of an essential section illustrating anoutput takeout structure in the automotive alternator according to aneighth embodiment of the present invention;

FIG. 11 is a perspective view showing a rectifying unit applied to aconventional automotive alternator; and

FIG. 12 is a sectional view of an essential section illustrating anoutput takeout structure in the conventional automotive alternator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following will describe the embodiments of the present invention inconjunction with the accompanying drawings.

First Embodiment

FIG. 1 is a sectional view showing an automotive alternator according toa first embodiment of the present invention. FIG. 2 is a perspectiveview showing a rectifying unit applied to the automotive alternatoraccording to the first embodiment of the present invention. FIG. 3 is asectional view of an essential section illustrating an output takeoutstructure in the automotive alternator according to the first embodimentof the present invention.

Referring to the FIGS. 1 through 3, the automotive alternator isconstituted by a case 3 composed of a front bracket 1 and a rear bracket2 made of aluminum, a shaft 6, which is provided in the case 3 and has apulley 4 secured to one end thereof, a Lundell-type rotor 7 secured tothe shaft 6, fans 5 secured to both axial ends of the rotor 7, a stator8 secured to the case 3 such that it surrounds the rotor 7, slip rings 9secured to the other end of the shaft 6 to supply electric current tothe rotor 7, a pair of brushes 10 sliding on the surface of the sliprings 9, a brush holder 11 accommodating the brushes 10, a rectifyingunit 12 electrically connected to the stator 8 to rectify thealternating current generated at the stator 8 into direct current, and aregulator 18 which is fitted to the brush holder 11, and adjusts themagnitude of the AC voltage generated at the stator 8.

The rotor 7 includes a field coil 13 generating magnetic fluxes uponpassage of electric current, and a pair of pole cores 14 and 15 whichare provided such that they cover the field coil 13, magnetic polesbeing formed into the pole cores 14 and 15 by the magnetic fluxes. Thepair of pole cores 14 and 15 has claw-shaped magnetic poles 14 a and 15a that are made of iron, have substantially trapezoidal outermostdiametral surfaces, and are protuberantly provided on the outerperipheral edge portions thereof at equiangular pitches. The pair ofpole cores 14 and 15 is secured to the shaft 6 such that the claw-shapedmagnetic poles 14 a and 15 a are opposed to engage each other.

The stator 8 is constructed by a cylindrical stator iron core 16composed of laminated magnetic steel plates, and a stator winding 17wound about the stator iron core 16. The stator 8 is clamped by thefront bracket 1 and the rear bracket 2 such that a uniform air gap isformed between the outer peripheral surfaces of the claw-shaped magneticpoles 14 a and 15 a and the inner peripheral surface of the stator ironcore 16.

Referring to FIG. 2, the rectifying unit 12 is constructed by aplurality of positive-electrode-side diodes 20 andnegative-electrode-side diodes 21 for carrying out full-waverectification on three-phase alternating current, a first cooling plate22 and a second cooling plate 23 for cooling the positive-electrode-sidediodes 20 and the negative-electrode-side diodes 21, respectively,insulators 24 for insulating the first and second cooling plates 22 and23, a circuit board 25, and an output terminal 26.

The first cooling plate 22 is shaped like a horseshoe, and has thepositive-electrode-side diodes 20 arranged on a main surface 22 athereof in the circumferential direction. A radiating fin 22 b isvertically installed from the rear surface of the first cooling plate22, that is, the surface on the opposite side from the main surface.Three flanges 30, 31, and 32 are provided at both ends and the middle,respectively, in the circumferential direction of the first coolingplate 22. The flange 30 provided at one circumferential end of the firstcooling plate 22 is raised from the main surface 22 a of the firstcooling plate 22, then extended outward in the radial direction and alsoextended outward in the circumferential direction. A mounting screwinsertion through hole 33 is provided at the radially extended endthereof, and an output terminal insertion through hole 34 is provided inthe circumferentially extended end thereof. The remaining flanges 31 and32 are raised from the main surface 22 a of the first cooling plate 22,then extended outward in the radial direction, and mounting screwinsertion through holes (not shown) are provided in the radiallyextended ends thereof.

The second cooling plate 23, which is also shaped like a horseshoe, hasa larger diameter than that of the first cooling plate 22, and has thenegative-electrode-side diodes 21 arranged on a main surface 23 athereof in the circumferential direction. Furthermore, three mountingscrew insertion through holes 35 are provided at both ends and themiddle in the circumferential direction of the second cooling plate 23such that they align with the mounting screw insertion through holes 33provided in the first cooling plate 22.

The circuit board 25 is a resinous molding having insert-molded wiringfor constituting diode bridges for the positive-electrode-side diodes 20and the negative-electrode-side diodes 21, and horseshoe-shaped like thesecond cooling plate 23. Three mounting screw insertion through holes 36are provided at both ends and the middle in the circumferentialdirection of the circuit board 25 such that they align with the mountingscrew insertion through holes 33 provided in the first cooling plate 22,respectively. Furthermore, an output terminal insertion through hole 37is provided in one circumferential end of the circuit board 25 such thatit aligns with the output terminal insertion through hole 34 provided inthe first cooling plate 22.

Each of the cylindrically shaped insulators 24 is made of, for example,a phenol resin, and has a flange 24 a in the central portion of theouter periphery thereof. The output terminal 26 has a knurl grooveportion 26 a provided at the counter-takeout side and an external threadportion 26 b provided at the takeout side.

The rectifying unit 12 is assembled as described below. First, theinsulators 24 are inserted in the mounting screw insertion through holes35 of the second cooling plate 23 such that the flanges 24 a are incontact with the main surface 23 a. Then, the first cooling plate 22 isdisposed such that the insulators 24 are inserted in the mounting screwinsertion through holes 33. This concentrically arranges the first andsecond cooling plates 22 and 23, respectively, with their main surfaces22 a and 23 a being flush with each other, and thepositive-electrode-side diodes 20 and the negative-electrode-side diodes21 facing each other. The circuit board 25 is stacked on the mainsurface 23 a of the second cooling plate 23 such that the insulators 24are inserted in the mounting screw insertion through holes 36. Thus,connecting terminals 25 a of the circuit board 25 are held betweenterminals 20 a and 21 a of the opposing positive-electrode-side andnegative-electrode-side diodes 20 and 21, respectively, and joined bysoldering. Subsequently, the output terminal 26 is inserted from theoutput terminal insertion through hole 37 of the circuit board 25 intothe output terminal insertion through holes 34 of the first coolingplates 22. Lastly, the knurl groove portion 26 a of the output terminal26 is press-fitted into the output terminal insertion through hole 34 ofthe first cooling plate 22 to electrically connect the output terminal26 and the first cooling plate 22, thus completing the assembly of therectifying unit 12 shown in FIG. 2.

In the rectifying unit 12 assembled as described above, a mounting screw40 inserted in the mounting screw insertion through holes 33, 35, and 36is fastened into a tapped hole 2 a provided in a rear bracket 2 so as tofasten together the first and second cooling plates 22 and 23, and thecircuit board 25, as illustrated in FIG. 3. The takeout end of theoutput terminal 26 connected to the first cooling plate 22 is extendedout of an opening 2 b provided in the rear bracket 2. An insulating bush41 formed of a phenol resin is mounted at the opening 2 b.

To join a vehicular connecting terminal 42 to the output terminal 26, acylindrical metal bush 43 is first loosely inserted in the insulatingbush 41 from the takeout end of the output terminal 26 and externallyfitted to the output terminal 26, then the connecting terminal 42 isexternally fitted to the takeout end of the output terminal 26, and anut 44 is threadably attached to the external thread portion 26 b. Then,the nut 44 is tightened so as to abut the other end of the metal bush 43against the rear surface of the first cooling plate 22, thus fasteninglysecuring the connecting terminal 42 between the nut 44 and one endsurface of the metal bush 43. In this case, one end surface of the metalbush 43 serves as a fastening seat.

Furthermore, a large-diameter lange 43 a is provided on one end of themetal bush 43, an axial gap being provided between the other end surfaceof the flange 43 a and the insulating bush 41. If the output terminal 26is axially displaced, then the other end surface of the flange 43 aabuts against the insulating bush 41 thereby to prevent any furtheraxial displacement, thus making up an axial displacement restrictingmember.

In the automotive alternator constructed as set forth above, electriccurrent is supplied from a battery (not shown) to the field coil 13through the brushes 10 and the slip rings 9, producing magnetic fluxes.The claw-shaped magnetic poles 14 a of the pole core 14 are magnetizedinto North-seeking (N) poles, while the claw-shaped magnetic poles 15 aof the pole core 15 are magnetized into South-seeking (S) poles.

On the other hand, the pulley 4 is driven by an engine, and the rotor 7is rotates by the shaft 6. The rotation of the rotor 7 causes a rotatingmagnetic field in the stator iron core 16, so that an electromotiveforce is generated in the stator winding 17. The AC electromotive forcegenerated in the stator 8 is rectified into direct current by therectifying unit 12, and the magnitude of the output voltage thereof isadjusted by the regulator 18. Then, the output of the rectifying unit 12is charged into the battery via the output terminal 26 and the vehicularconnecting terminal 42.

According to the first embodiment, the fastening force of the nut 44 isreceived by the rear surface of the first cooling plate 22 via the metalbush 43 constituting the fastening seat, permitting the fastening forcefor the vehicular connecting terminal 42 to be secured.

Moreover, if the output terminal 26 is axially displaced, the other endsurface of the flange 43 a of the metal bush 43 abuts against theinsulating bush 41, thereby preventing further axial displacement of theoutput terminal 26. Therefore, even if the vibrations of a weight, suchas a harness, from a vehicle is transmitted to the vehicular connectingterminal 42, the axial displacement of the output terminal 26 isrestrained to protect the rectifying unit 12 from damage or the fastenedportion of the mounting screw 40 from breakage.

When the automotive alternator generates power, large current passes thevehicular connecting terminal 42, generating heat. However, the gapformed between the metal bush 43 and the insulating bush 41 causes lessheat to be conducted from the metal bush 43 to the insulating bush 41,thus controlling a rise in the temperature of the insulating bush 41. Asa result, the thermal degradation of the insulating bush 41 can berestrained. This means that the shrinkage of the insulating bush 41attributable to the thermal degradation of the insulating bush 41 issuppressed, and the axial displacement of the output terminal 26 iscontrolled to a predetermined range, leading to improved reliability.

In addition, since the insulating bush 41 is not involved in thefastening mechanism for the vehicular connecting terminal 42, theoccurrence of the thermal shrinkage of the insulating bush 41 caused bythermal degradation will not lead to loosening of the vehicularconnecting terminal 42. This will secure the fastening force for thevehicular connecting terminal 42 for a long time, with resultant higherreliability. An increase in the contact resistance produced between thevehicular connecting terminal 42 and the output terminal 26 attributableto the loosening of the vehicular connecting terminal 42 can berestrained, so that no significant heat generation will take place atthe fastened portion of the connecting terminal 42, while significantheat generation used to take place in the conventional structure. Inthis aspect also, the thermal degradation of the insulating bush 41 canbe suppressed. With this arrangement, the shrinkage of the insulatingbush 41 resulting from the thermal degradation of the insulating bush 41is controlled, so that the axial displacement of the output terminal 26is limited to a predetermined range, leading to higher reliability.

Second Embodiment

Referring to FIG. 4, in a second embodiment, an elastic member 45composed of a silicone rubber or the like is interposed between aninsulating bush 41 and a flange 43 a of a metal bush 43, a support wall2 c is vertically provided outside the counter-takeout end of an outputterminal 26 from the inner wall surface of a rear bracket 2, and aninsulating member 46 formed of a phenol resin or the like is interposedbetween a counter-takeout end surface of the output terminal 26 and thesupport wall 2 c. The rest of the construction of the second embodimentis the same as the construction of the first embodiment described above.

The second embodiment provides the advantage described below in additionto the advantage of the above first embodiment. Because of the presenceof the elastic member 45 interposed between the insulating bush 41 andthe flange 43 a of the metal bush 43, even if the vibrations due to aweight, such as a harness, from a vehicle is transmitted to thevehicular connecting terminal 42, the stress applied to the rectifyingunit 12 via the output terminal 26 will be absorbed by the elasticmember 45. This arrangement makes it possible to protect the rectifyingunit 12 from damage or the fastened portion of a mounting screw 40 frombreakage attributable to the vibrations caused by a weight, such as aharness, from a vehicle.

Moreover, the presence of the insulating member 46 interposed betweenthe support wall 2 c vertically provided from the inner wall surface ofthe rear bracket 2 and the counter-takeout end surface of the outputterminal 26 securely restrains the axial displacement of the outputterminal 26 attributable to the vibrations caused by a weight, such as aharness, from the vehicle. This will securely prevents damage to therectifying unit 12 or breakage of a fastened portion of a mounting screw40.

Third Embodiment

In a third embodiment shown in FIG. 5, an elastic member 47 composed ofsilicone rubber or the like is employed in place of the insulating bush41. The elastic member 47 is installed at an opening 2 b of a rearbracket 2 such that it abuts against the other end surface of a flange43 a of the metal bush 43. The rest of the construction of the thirdembodiment is the same as the construction of the first embodimentdescribed above.

In the third embodiment, the axial displacement of an output terminal 26is restricted by the elastic member 47, and the stress applied to arectifying unit 12 via the output terminal 26 is absorbed by the elasticmember 47. Thus, the third embodiment permits enhanced prevention ofdamage to the rectifying unit 12 or breakage of the fastened portion ofa mounting screw 40, thus enabling higher reliability to be achieved.

Fourth Embodiment

In a fourth embodiment shown in FIG. 6, a cylindrical metal bush 48 isused in place of the metal bush 43. The metal bush 48 is fasteninglysecured to the rear surface of the first cooling plate 22 by a metalbush fastening nut 49. Furthermore, a vehicular connecting terminal 42is fasteningly fixed to the outer end surface of the metal bushfastening nut 49 by a nut 44. The axial position restricting member isformed by the metal bush 48 and the metal bush fastening nut 49, theouter end surface of the metal bush fastening nut 49 constituting afastening seat. The rest of the construction of the fourth embodiment isthe same as the construction of the third embodiment set forth above.

In the fourth embodiment, the fastening force of the nut 44 is receivedby the rear surface of a first cooling plate 22 via the metal bushfastening nut 49 constituting the fastening seat and the metal bush 48.If an output terminal 26 is axially displaced, then the other endsurface of the metal bush fastening nut 49 abuts against an elasticmember 47 so as to prevent further axial displacement of the outputterminal 26. Hence, the fourth embodiment provides the same advantage asthat of the third embodiment.

Fifth Embodiment

In the above fourth embodiment, the output terminal 26 is taken out inthe axial direction of the automotive alternator. In a fifth embodiment,the circumferentially extended portion of a flange 30 of a first coolingplate 23 is bent into an L shape, and the output terminal 26 is takenout in the radial direction of the automotive alternator, as shown inFIG. 7, to provide the same advantage.

Sixth Embodiment

In a sixth embodiment shown in FIG. 8, a large-diameter flange 26 cfunctioning as the axial displacement restricting member is formed atthe proximal end of an external thread portion 26 b of an outputterminal 26A. The rest of the construction of the sixth embodiment isthe same as the construction of the fourth embodiment set forth above.

In the sixth embodiment, a vehicular connecting terminal 42 isfasteningly secured to the outer end surface, i.e., the fastening seat,of the flange 26 c by a nut 44. The inner end surface of the flange 26 cabuts against an elastic member 47 to restrict the axial displacement ofthe output terminal 26A. Thus, the sixth embodiment provides the sameadvantage as that of the fourth embodiment, and permits reduced costbecause it obviates the need for the metal bush 43.

Seventh Embodiment

In a seventh embodiment shown in FIG. 9, a nut 51 serving as a fasteningseat is threadably attached at a position spaced away from an outputterminal fastening nut 50 of an external thread portion 26 b of anoutput terminal 26, and a connecting terminal 42 is fasteningly securedto the nut 51 by a nut 44. The rest of the construction of the seventhembodiment is the same as the construction of the conventional exampleshown in FIG. 11 and FIG. 12.

In the assembly structure of a rectifying unit 12A according to theseventh embodiment, the nut 51 to which the connecting terminal 42 isfastened is spaced away from the output terminal fastening nut 50, andthreadably attached to the external thread portion 26 b.

With this arrangement, even if an insulating bush 41 develops thermaldegradation due to the heat generated at the connecting terminal 42,causing the output terminal fastening nut 50 to loosen, the connectingterminal 42 fastened by the nuts 44 and 51 will not loosen. As a result,significant heat generation caused by loosening of the fastened portionof the connecting terminal 42 is suppressed, so that the axialdisplacement of the output terminal 26 will not be expedited. Thus, ascompared with the conventional example, there will be less chance of theoccurrence of damage to the rectifying unit 120 or breakage of thefastened portion of the mounting screw 40 attributable to the vibrationsdue to a weight, such as a harness, from the vehicle. The result ishigher reliability.

Furthermore, the fastening force of the nut 44 is received by the nut 51spaced away from the output terminal fastening nut 50 that pushes aninsulating bush 41. Hence, the vibrations due to a weight, such as aharness, from the vehicle are not directly applied to the insulatingbush 41, making it possible to restrain the occurrence of the creep ofthe insulating bush 41.

Eighth Embodiment

In an eighth embodiment, an output terminal 26B is employed in place ofthe output terminal 26. Referring to FIG. 10, the output terminal 26Bhas a first external thread portion 26 d having a large diameter and asecond external thread portion 26 e having a small diameter, which areformed at the takeout end thereof A stepped portion 26 f formed at thejoint of the external thread portions 26 d and 26 e constitutes afastening seat. A connecting terminal 42 is fasteningly secured to thestepped portion 26 f by a nut 44. The rest of the construction of theeighth embodiment is the same as the construction of the seventhembodiment set forth above.

In the assembly structure of a rectifying unit 12A according to theeighth embodiment, the stepped portion 26 f to which the connectingterminal 42 is fasteningly secured is formed on the output terminal 26B,being spaced away from an output terminal fastening nut 50.

With this arrangement, even if an insulating bush 41 develops thermaldegradation due to the heat generated at the connecting terminal 42,causing the output terminal fastening nut 50 to loosen, the connectingterminal 42 fastened by the nuts 44 will not loosen. In addition, thefastening force of the nut 44 is received by the stepped portion 26 fspaced away from the output terminal fastening nut 50 pushing theinsulating bush 41; therefore, the vibrations caused by a weight, suchas a hardness, from the vehicle are not directly applied to theinsulating bush 41.

Accordingly, the eighth embodiment provides the same advantage as thatof the seventh embodiment set forth above.

In the embodiments described above, the output terminal 26 has beenelectrically connected to the first cooling plate 22, and the secondcooling plate 23 has been electrically connected to the rear bracket 2.The same advantages, however, can be obtained when the output terminal26 is electrically connected to the second cooling plate 23, and thefirst cooling plate 22 is electrically connected to the rear bracket 2.

In the first through fifth embodiments discussed above, the metal bushhas been used as the axial displacement restricting member. The bush,however, is not limited to a metal one; it may alternatively be aceramic bush.

Although the preferred embodiments of the present invention have beendescribed above, it should be understood that the present invention isnot limited thereto and that other modifications will be apparent tothose skilled in the art without departing from the sprint of theinvention.

The scope of the present invention, therefore, should be determinedsolely by the appended claims.

This automotive alternator of the present invention is constituted asdescribed above. Thus, this automotive alternator has the followingeffects.

To these ends, according to one aspect of the present invention, thereis provided an automotive alternator including a rotor rotatablysupported in a metal bracket, a stator secured to the bracket such thatit is located around the outer periphery of the rotor to surround therotor, a rectifying unit having a first cooling plate on which aplurality of first diodes are provided, and a second cooling plate onwhich a plurality of second diodes of the opposite polarity from that ofthe first diodes are provided, the second cooling plate beingelectrically connected to the bracket, and the first and second coolingplates being secured to an inner wall surface of the bracket, a resinousinsulating bush mounted at an opening provided in the bracket, an outputterminal which is electrically connected to the first cooling plate,loosely inserted in the insulating bush, and taken out of the bracket, avehicular connecting terminal being connected to the takeout end of theoutput terminal, an axial displacement restricting member which engagesthe insulating bush thereby to restrict the axial displacement of theoutput terminal, and constitutes a fastening seat, and an externalthread portion provided on the takeout end of the output terminal,wherein the counter-takeout end of the output terminal is secured to thefirst cooling plate, and the vehicular connecting terminal isfasteningly secured to the fastening seat of the axial displacementrestricting member by a nut threadably attached to the external threadportion. With this arrangement, the fastening force for the vehicularconnecting terminal can be secured for an extended period of time,marked heat generation attributable to the loosening of the fastenedvehicular connecting terminal can be restrained, and the axialdisplacement of the output terminal can be restrained, allowing anautomotive alternator featuring high reliability to be achieved.

Preferably, an elastic member is interposed between the axialdisplacement restricting member and the insulating bush. With thisarrangement, the vibrations transmitted to the output terminal via thevehicular connecting terminal are absorbed by the elastic member, thusminimizing the chance of damage to the rectifying unit.

Preferably, the insulating bush is mounted at the opening of the bracketsuch that it is abutted against the axial displacement restrictingmember, and the insulating bush is formed of an elastic material. Withthis arrangement, the vibrations transmitted to the output terminal viathe vehicular connecting terminal are absorbed by the insulating bush,thus minimizing the chance of damage to the rectifying unit.

Alternatively, the axial displacement restricting member is externallyfitted to the output terminal, and composed of a cylindrical metal bushhaving a flange of a large diameter on one end thereof, one end surfaceof the metal bush abuts against the vehicular connecting terminal, andthe other end surface thereof abuts against the first cooling plate, andthe flange thereof engages the insulating bush to restrain the axialdisplacement of the output terminal when the vehicular connectingterminal is connected to the takeout end of the output terminal. Thisarrangement secures the fastening force for the vehicular connectingterminal for an extended period of time, and also restrains the axialdisplacement of the output terminal.

Alternatively, the axial displacement restricting member is constructedby a metal bush fastening nut threadably attached to the external threadportion of the output terminal, a cylindrical metal bush which isexternally fitted to the output terminal and fasteningly secured to thefirst cooling plate by the metal bush fastening nut, the vehicularconnecting terminal is fasteningly secured to the outer end surface ofthe metal bush fastening nut by the nut threadably attached to theexternal thread portion, and the inner end surface of the metal bushfastening nut engages the insulating bush thereby to restrain the axialdisplacement of the output terminal. This arrangement secures thefastening force for the vehicular connecting terminal for an extendedperiod of time, and also restrains the axial displacement of the outputterminal.

Preferably, the axial displacement restricting member is constituted bya large-diameter flange formed at the proximal end of the externalthread portion of the output terminal, the vehicular connecting terminalis fasteningly secured to the outer end surface of the flange by the nutthreadably attached to the external thread portion, and the inner endsurface of the flange engages the insulating bush thereby to restrainthe axial displacement of the output terminal. With this arrangement,the axial displacement restricting member can be accomplished using asimple construction.

Preferably, a support wall is vertically provided such that it opposesthe counter-takeout end surface of the output terminal, and aninsulating member is interposed between the support wall and thecounter-takeout end surface of the output terminal. This arrangementsecurely suppresses the axial displacement of the output terminal.

According to another aspect of the present invention, there is providedan automotive alternator including a rotor rotatably supported in ametal bracket, a stator secured to the bracket such that it is locatedaround the outer periphery of the rotor to surround the rotor, arectifying unit having a first cooling plate on which a plurality offirst diodes are provided, and a second cooling plate on which aplurality of second diodes of the opposite polarity from that of thefirst diodes are provided, the second cooling plate being electricallyconnected to the bracket, and the first and second cooling plates beingsecured to an inner wall surface of the bracket, a resinous insulatingbush mounted at an opening provided in the bracket, an output terminalwhich is electrically connected to the first cooling plate, looselyinserted in the insulating bush, and taken out of the bracket, avehicular connecting terminal being connected to the takeout end of theoutput terminal, through holes which are provided in the first andsecond cooling plates and in which the output terminal is inserted, anexternal thread portion provided on the takeout end of the outputterminal, an output terminal fastening nut threadably attached to theexternal thread portion to fasteningly secure the output terminal to thebracket, and a fastening seat provided at a position different from thatof the output terminal fastening nut on the takeout end of the outputterminal, wherein the counter-takeout end of the output terminal isinserted in the through holes of the first and second cooling plates andsecured to the first cooling plate, the first and second cooling platesare secured together with the insulating bush to the bracket by theoutput terminal fastening nut, and the vehicular connecting terminal isfasteningly secured to the fastening seat by a nut threadably attachedto the external thread portion. With this arrangement, the fasteningforce for the vehicular connecting terminal can be secured for anextended period of time, and marked heat generation attributable to theloosening of the fastened vehicular connecting terminal can berestrained, allowing an automotive alternator featuring high reliabilityto be achieved.

Preferably, the external thread portion of the output terminal iscomposed of a first external thread portion having a large diameter towhich the output terminal fastening nut threadably attached and a secondexternal thread portion having a small diameter which is continuouslyformed at the takeout end of the first external thread portion and towhich the nut is threadably attached, and a stepped portion formed inthe area, where the first and second external thread portions areconnected, constitutes the fastening seat. This arrangement secures thefastening force for the vehicular connecting terminal for an extendedperiod of time.

What is claimed is:
 1. An automotive alternator comprising: a rotorrotatably supported in a metal bracket; a stator secured to the bracketsuch that it is located around the outer periphery of the rotor tosurround the rotor; a rectifying unit having a first cooling plate onwhich a plurality of first diodes are provided, and a second coolingplate on which a plurality of second diodes of the opposite polarityfrom that of the first diodes are provided, the second cooling platebeing electrically connected to the bracket, and the first and secondcooling plates being secured to an inner wall surface of the bracket; aresinous insulating bush mounted at an opening provided in the bracket;an output terminal which is electrically connected to the first coolingplate, loosely inserted in the insulating bush, and taken out of thebracket, a vehicular connecting terminal being connected to the takeoutend of the output terminal; through holes which are provided in thefirst and second cooling plates and in which the output terminal isinserted; an external thread portion provided on the takeout end of theoutput terminal; an output terminal fastening nut threadably attached tothe external thread portion to fasteningly secure the output terminal tothe bracket; and a fastening seat provided at a position different fromthat of the output terminal fastening nut on the takeout end of theoutput terminal, wherein the counter-takeout end of the output terminalis inserted in the through holes of the first and second cooling platesand secured to the first cooling plate, the first and second coolingplates are secured together with the insulating bush to the bracket bythe output terminal fastening nut, and the vehicular connecting terminalis fasteningly secured to the fastening seat by the nut threadablyattached to the external thread portion.
 2. An automotive alternatoraccording to claim 1, wherein the external thread portion of the outputterminal is composed of a first external thread portion having a largediameter to which the output terminal fastening nut is threadablyattached and a second external thread portion having a small diameterwhich is continuously formed at the takeout end of the first externalthread portion and to which the nut is threadably attached, and astepped portion formed in the area where the first and second externalthread portions are connected constitutes the fastening seat.
 3. Anautomotive alternator comprising: a rotor rotatably supported in a metalbracket; a stator secured to the bracket such that it is located aroundthe outer periphery of the rotor to surround the rotor; a rectifyingunit having a first cooling plate on which a plurality of first diodesare provided, and a second cooling plate on which a plurality of seconddiodes of the opposite polarity from that of the first diodes areprovided, the second cooling plate being electrically connected to thebracket, and the first and second cooling plates being secured to aninner wall surface of the bracket; a resinous insulating bush mounted atan opening provided in the bracket; an output terminal which iselectrically connected to the first cooling plate; a vehicularconnecting terminal which is connected to a takeout end of the outputterminal; through holes which are provided in the first and secondcooling plates and in which the output terminal is inserted; an externalthread portion provided on the takeout end of the output terminal; anoutput terminal fastening nut threadably attached to the external threadportion to fasteningly secure the output terminal to the bracket; and afirst nut threadably attached at a position spaced away from the outputterminal fastening nut, wherein the counter-takeout end of the outputterminal is inserted in the through holes of the first and secondcooling plates and secured to the first cooling plate, the first andsecond cooling plates are secured together with the insulating bush tothe bracket by the output terminal fastening nut, and the vehicularconnecting terminal is fasteningly secured to said first nut by a secondnut threadably attached to the external thread portion.
 4. Thealternator of claim 3, wherein the first nut serves as a fastening seat.